1. Field of the Invention
The invention relates in general to engine compensators and, in particular, to an improved engine compensator capable of repeatedly and reliably absorbing the high rotational shock loads delivered through a drive train by high performance engines. Compared to conventional compensators, the compensator of the present invention comprises fewer parts, weighs less, is less expensive to manufacture, and uniquely provides simultaneous compensating rotation and axial movement of the compensator output ring member.
2. Description of the Prior Art
An engine compensator is a mechanism that transmits rotational loads between an input shaft and an output ring member while also providing compensating rotation of the output ring member relative to an input shaft. Typically, the input shaft is the crankshaft of an engine. This compensating rotation, or "give", is often needed in order to absorb rotational shock loads. In many industries, compensators are desired for their ability to provide smooth power delivery. Compensators are often required to reliably protect transmission gears, sprockets, chains and other drive train elements from failure due to spike loads delivered to the drive train system. This type of failure is of particular concern in the motorcycle industry where large spike loads from the engine are delivered to the drive train during shifting, accelerating, and decelerating. These spike loads are particularly severe in racing conditions where, as often times occurs, the clutch is abused during shifting. This abuse occurs when the clutch is rapidly re-engaged when the engine RPM is significantly greater than the input RPM desired by the drive train or system. The same abuse occurs during deceleration, that is, when the engine RPM is significantly less than the input RPM desired by the drive system when the clutch is rapidly re-engaged.
Approximately during the 1930's the manufacturer of Harley-Davidson Motorcycles developed a highly successful engine compensator which to this day has essentially remained unchanged. The compensator weighs approximately 6 lbs 1/8 oz and was originally designed for V-twin four stroke engines of around 750 to 880 cubic centimeter capacity. These engines initially produced approximately 38 to 40 horsepower. The prior art compensator for these engines comprises a plurality of components, and the compensating action of the mechanism is achieved by the use of belleville springs that are configured to absorb the rotational spike loads. The prior art compensator functions satisfactorily as long as spike loads remain less than about 130 ft-lbs, which is generally the case for 38 to 40 horsepower engines.
Many disadvantages of the prior art compensators become apparent when they are used in drive trains where the horsepower of the engine substantially exceeds 40 horsepower. Today it has become commonplace to modify, for example, motorcycle engines to achieve power ratings of 100 horsepower or greater. As the horsepower increases, so do the rotational spike loads imposed on the components of the drive system. Under high performance conditions, these spike loads can easily exceed 130 ft-lbs. The prior art compensator is unable to consistently and reliably absorb these increased rotational shock loads. The belleville springs in the prior art compensator often break, causing the compensator to slip. When the compensator slips, rotational loads can no longer be transmitted through the mechanism. Attempts have been made to add additional belleville spring washers to the prior art compensator to correct this problem, however the rotational shock loads of these high performance engines still cause spring failure. A common, but undesirable, solution often employed by users to overcome this problem is to weld the compensator mechanism solid. This not only eliminates the desirable compensating action of the mechanism, but also reduces the mechanism to the role of adding additional weight and rotational inertia to the engine. This unnecessary weight and inertia is highly undesirable in high performance applications.
Prior engine compensators that were proposed for use with high performance motorcycle engines generally could not consistently and reliably absorb rotational shock loads in excess of approximately 130 ft-lbs.
Thus, those concerned with these problems recognize the need for an improved engine compensator capable of consistently and reliably absorbing the increased rotational shock loads that are associated with high performance engines. Those skilled in the art also recognize the need for such a compensator to comprise as few parts as possible, be simple to manufacture, be lightweight, and add as little rotational inertia to the drive train as possible.
These and other difficulties of the prior art have been overcome according to the present invention.